The invention relates to a device for air flow rate measurement in the air intake tube of an internal combustion engine having at least two temperature-dependent hot wire resistors in different branches of a bridge, circuit having closed-loop electric current control.
A device is known (German Pat. No. 20 42 983) which has two temperature-dependent resistors in different bridge branches of a measurement bridge. In this device, one of the two temperature-dependent resistors is intended to detect the air throughput and the other resistor is intended to influence the measurement result in the sense of making a correction dependent on the aspirated air temperature. In the publication of the known air flow rate measuring device, it is expressly stated that the temperature-dependent resistor for detecting the aspirated air temperature should be held to the particular temperature value of the air flowing past it; that is, it has no heat output of its own. Because of the geometric embodiment and electric circuitry of the known air flow rate measuring device, there are sizable differences between the thermal time constants of the hot wire and of the temperature probe. When the aspirated air temperature changes, as does occur in actual driving operation, these differences cause relatively large errors in measurement.